Greater fatigability in knee-flexors vs. knee-extensors after a standardized fatiguing protoco

The present study aimed to investigate the effects of a standardized fatiguing protocol on central and peripheral fatigue in knee-flexors and knee-extensors. Thirteen healthy men (age: 23\u2009\ub1\u20093 years; height: 1.78\u2009\ub1\u20090.09 m; body-mass: 73.6\u2009\ub1\u20099.2\u2005kg) volunteered for the present study. Maximal voluntary contraction (MVC), Electromyography (EMG) activity, voluntary activation level (VAL) as an index of central fatigue and twitch potentiation as an index of peripheral fatigue were measured before and after the fatiguing protocol. The fatiguing protocol consisted of a 0.6 duty-cycle to exhaustion (6\u2005s isometric contraction, 4\u2005s recovery) at 70% MVC. After the fatiguing protocol, MVC decreased in both (Effect-size (ES)\u2009=\u20091.14) and knee-extensors (ES\u2009=\u20091.14), and EMG activity increased in both knee-flexors (ES\u2009=\u20092.33) and knee-extensors (ES\u2009=\u20091.54). Decreases in VAL occurred in knee-flexors (ES\u2009=\u20090.92) but not in knee-extensors (ES\u2009=\u20090.04). Decreases in potentiation occurred in both knee-flexors (ES\u2009=\u20090.84) and knee-extensors (ES\u2009=\u20090.58). The greater central occurrence of fatigue in knee-flexors than in knee-extensors may depend on the different muscle morphology and coupled with a greater tolerance to fatigue in knee-extensors. The present data add further insight to the complicated knee-flexors-to-knee-extensors strength relationship and the mechanisms behind the different occurrence of fatigue

Influence of dietary conjugated linoleic acid on growth, meat quality, lipogenesis, plasma leptin and physiological variables of lipid metabolism in rabbits

We investigated the effects of conjugated linoleic acid (CLA) supplementation on growth, feed efficiency, carcass characteristics, meat quality, lipogenesis, and lipid metabolism in rabbits. One hundred forty-four New Zealand White rabbits, half males, half females, age 55 d, mean 1.8 kg BW, were randomly assigned to three weight- and sex-balanced feeding groups in which conventional pelleted diets were supplemented with 0, 0.25, or 0.5% of a CLA preparation. The CLA preparation contained 65% CLA isomers. Twelve rabbits (six males and six females from each group) were slaughtered at each of three slaughtering trials (2.5, 2.8, and 3.1 kg BW, or 76, 90, and 104 d of age). Conjugated linoleic acid supplementation did not influence growth performance (P > or = 0.05) or carcass characteristics but reduced perirenal fat at heavier slaughtering weights (P = 0.09 at 2.8 kg BW; P < 0.01 at 3.1 kg BW). Conjugated linoleic acid reduced acetyl-CoA-carboxylase (CBX) activity in liver (P < 0.05) and adipose tissues (P < 0.01) but did not influence malic enzyme (ME) or glucose-6-phosphate dehydrogenase activity. Significant differences were found between sex in interscapular fat (P < 0.05) for CBX, in perirenal (P < 0.01) and interscapular (P < 0.05) fat for ME, and a tendency (P = 0.070) in liver for glucose-6-phosphate dehydrogenase. The oxidative stability of longissimus lumborum muscle was increased at the higher level of supplementation (P < 0.05). Conjugated linoleic acid reduced (P < 0.05) triglycerides and total cholesterol in plasma with a trend to increased serum leptin (P = 0.06). Plasma triglycerides were higher in males than females (P < 0.01) and plasma leptin tended to be higher in females (2.57 vs. 2.13 ng/ml, P = 0.06). It is concluded that dietary CLA reduced carcass fat in rabbits slaughtered at 2.8 kg or above and altered lipid metabolism to produce lower concentrations of serum triglycerides and total cholesterol and higher concentrations of leptin

Giant viral signatures on the Greenland ice sheet

Background Dark pigmented snow and glacier ice algae on glaciers and ice sheets contribute to accelerating melt. The biological controls on these algae, particularly the role of viruses, remain poorly understood. Giant viruses, classified under the nucleocytoplasmic large DNA viruses (NCLDV) supergroup (phylum Nucleocytoviricota), are diverse and globally distributed. NCLDVs are known to infect eukaryotic cells in marine and freshwater environments, providing a biological control on the algal population in these ecosystems. However, there is very limited information on the diversity and ecosystem function of NCLDVs in terrestrial icy habitats. Results In this study, we investigate for the first time giant viruses and their host connections on ice and snow habitats, such as cryoconite, dark ice, ice core, red and green snow, and genomic assemblies of five cultivated Chlorophyta snow algae. Giant virus marker genes were present in almost all samples; the highest abundances were recovered from red snow and the snow algae genomic assemblies, followed by green snow and dark ice. The variety of active algae and protists in these GrIS habitats containing NCLDV marker genes suggests that infection can occur on a range of eukaryotic hosts. Metagenomic data from red and green snow contained evidence of giant virus metagenome-assembled genomes from the orders Imitervirales, Asfuvirales, and Algavirales. Conclusion Our study highlights NCLDV family signatures in snow and ice samples from the Greenland ice sheet. Giant virus metagenome-assembled genomes (GVMAGs) were found in red snow samples, and related NCLDV marker genes were identified for the first time in snow algal culture genomic assemblies; implying a relationship between the NCLDVs and snow algae. Metatranscriptomic viral genes also aligned with metagenomic sequences, suggesting that NCLDVs are an active component of the microbial community and are potential “top-down” controls of the eukaryotic algal and protistan members. This study reveals the unprecedented presence of a diverse community of NCLDVs in a variety of glacial habitats dominated by algae

Endometabolic profiling of pigmented glacier ice algae: the impact of sample processing

Introduction Glacier ice algae, mainly Ancylonema alaskanum and Ancylonema nordenskiöldi, bloom on Greenland Ice Sheet bare ice surfaces. They significantly decrease surface albedo due to their purple-brown pigmentation, thus increasing melt. Little is known about their metabolic adaptation and factors controlling algal growth dynamics and pigment formation. A challenge in obtaining such data is the necessity of melting samples, which delays preservation and introduces bias to metabolomic analysis. There is a need to evaluate the physiological response of algae to melting and establish consistent sample processing strategies for metabolomics of ice microbial communities. Objectives To address the impact of sample melting procedure on metabolic characterization and establish a processing and analytical workflow for endometabolic profiling of glacier ice algae. Methods We employed untargeted, high-resolution mass spectrometry and tested the effect of sample melt temperature (10, 15, 20 °C) and processing delay (up to 49 h) on the metabolome and lipidome, and complemented this approach with cell counts (FlowCam), photophysiological analysis (PAM) and diversity characterization. Results and Conclusion We putatively identified 804 metabolites, with glycerolipids, glycerophospholipids and fatty acyls being the most prominent superclasses (> 50% of identified metabolites). Among the polar metabolome, carbohydrates and amino acid-derivatives were the most abundant. We show that 8% of the metabolome is affected by melt duration, with a pronounced decrease in betaine membrane lipids and pigment precursors, and an increase in phospholipids. Controlled fast melting at 10 °C resulted in the highest consistency, and is our recommendation for future supraglacial metabolomics studies

The match-play sprint performance of elite senior hurlers during competitive games

The typical sprint profile in elite hurling has yet to be established. The purpose of this study was to investigate the sprinting demands of elite hurling competition and characterize the sprinting patterns of different playing positions. GPS (10-Hz, STATSports Viper) were used to collect data from 51 hurlers during 18 games. The total sprint ( 6522 km\ub7h-1) distance (TSD), the number of sprints (NOS) classified as length (&lt;20 m, 6520 m) and relative speed thresholds (&lt;80%, 80-90%, &gt;90%), the between-sprint duration and the number of repeated-sprint bouts ( 652 sprints in 6460 s) were analyzed. The NOS was 22.2 \ub1 6.8 accumulating 415 \ub1 140 m TSD. The NOS &lt;20 m, 6520 m was 14.0 \ub1 4.7 and 8.1 \ub1 3.6 respectively. The NOS &lt;80%, 80-90% and &gt;90% was 10.6 \ub1 4.3, 8.2 \ub1 3.6, 3.4 \ub1 2.4 respectively. The between-sprint duration and the repeated-sprint bouts were 208 \ub1 86 s and 4.5 \ub1 2.6 respectively. TSD (ES = -0.20), NOS (ES = -0.34), NOS &lt;20 m (ES = -0.33), 6520 m (ES = -0.24), 80-90% (ES = -0.35) &gt;90% (ES = -0.13) and repeated-sprint bouts (ES = -0.28) decreased between-halves. Full-backs performed a lower NOS &lt;80% than half-backs (ES = -0.66) and a shorter mean duration of sprints than half-backs (ES = -0.75), midfielders (ES = -1.00) and full-forwards (ES = -0.59). These findings provide a sprint profile of elite hurling match-play that coaches should consider to replicate the sprint demands of competition in training

Are there consistent relationships between major connective tissue components, intramuscular fat content and muscle fibre types in cattle muscle?

peer-reviewedIntramuscular connective tissue (IMCT) is mainly composed of several fibrils (known as total collagen (TCol)) linked between each other by different chemical cross-links (CLs), the whole being embedded in a matrix of proteoglycans (PGs). In the field of beef quality, there is limited information on the role of CLs and PGs. Accordingly, several authors suggest that, to investigate the role of IMCT, it is important to investigate them just like TCol and insoluble collagen (ICol). In muscle, there are two other components, the muscle fibres and intramuscular fat (IMF) content. There are limited data on the relationships between these three components of muscle and then on possibility to independently manipulate these characteristics in order to control the final quality of meat. The present study aimed to investigate whether consistent relationships exist between these different components of muscle. Therefore, the present study compared four muscles of two cattle types (dairy and beef) to determine associations between TCol, ICol, CLs and PGs. Data were analysed across and within muscle (M) and animal type (AT) based on residuals. There was a strong M and AT effect for all muscle characteristics and an interaction M × AT for type I muscle fibres and IMF. Correlations between TCol, ICol and their CLs were M- and AT-independent. Total proteoglycans were positively correlated with TCol and ICol in a muscle-dependent manner irrespective of AT, but no correlation was found with CLs. On the contrary, CLs were negatively correlated with the ratio TPGs : TCol in an M-dependent manner, irrespective of AT. TCol, ICol and CLs were positively and negatively correlated with type IIA and IIB+X muscle fibres only in longissimus thoracis (LT) muscle, regardless the AT. Insoluble collagen was the only parameter of IMCT to be correlated with type I muscle fibres but only in LT muscle, irrespective of AT. There was no correlation between PGs and muscle fibre types, but PGs were the only IMCT component to be related with IMF in an M-dependent manner, irrespective of AT. Finally, there was no correlation between muscle fibre types and IMF content within M and AT. This study revealed that there is a strong relationship between IMCT components irrespective of M, an M-dependent relationship between the IMCT components and muscle fibre types and few (only with PGs) or no relationship between IMF and IMCT and muscle fibres

Sprint start kinetics of amputee and non-amputee sprinters

The purpose of this study was to explore the relationship between the forces applied to the starting blocks and the start performances (SPs) of amputee sprinters (ASs) and non-amputee sprinters (NASs). SPs of 154 male and female NASs (100-m personal records [PRs], 9.58–14.00 s) and 7 male ASs (3 unilateral above knee, 3 unilateral below knee, 1 bilateral below knee; 100 m PRs, 11.70–12.70 s) with running specific prostheses (RSPs) were analysed during full-effort sprint starts using instrumented starting blocks that measured the applied forces in 3D. Using the NAS dataset and a combination of factor analysis and multiple regression techniques, we explored the relationship between force characteristics and SP (quantified by normalized average horizontal block power). Start kinetics were subsequently compared between ASs and NASs who were matched based on their absolute 100 m PR and their 100 m PR relative to the world record in their starting class. In NASs, 86% of the variance in SP was shared with five latent factors on which measured parameters related to force application to the rear and front blocks and the respective push-off directions in the sagittal plane of motion were loaded. Mediolateral force application had little influence on SP. The SP of ASs was significantly reduced compared to that of NASs matched on the basis of relative 100-m PR (−33.8%; d = 2.11, p < 0.001), while a non-significant performance reduction was observed when absolute 100-m PRs were used (−17.7%; d = 0.79, p = 0.09). These results are at least partially explained by the fact that force application to the rear block was clearly impaired in the affected legs of ASs